1. Field of the Invention
The present invention generally relates to an active device array substrate, and more particularly, to an active device array substrate with a test circuit.
2. Description of Related Art
Various displays have been quickly developed along with the advancement of photoelectronic and semiconductor technologies. Liquid crystal display (LCD) has been broadly applied and is about to replace the conventional cathode ray tube (CRT) as the mainstream among the next-generation displays.
In order to improve the yield of active device array substrate in LCD, an electrical test is usually carried out to devices or circuits on an active device array substrate right after the active device array substrate is fabricated to determine whether these devices or circuits work properly. In order to test the bonding state between a driving chip and bonding pads on an active device array substrate, a microscope is usually used to observe the bonding state between the driving chip and the bonding pads. However, such a technique is very time-consuming and may produce human errors. Thereby, a design of disposing a circuit with an electrical test function in a peripheral circuit area of an active device array substrate is provided.
FIG. 1 is a partial top view of a conventional active device array substrate. Referring to FIG. 1, the active device array substrate 100 includes an active matrix device 110 disposed in the display area I′ and a plurality of first bonding pads 120a, 120b, 120c, . . . , a plurality of second bonding pads 130a, 130b, 130c, . . . , a test signal pad 160, and a driving chip (not shown) disposed in the peripheral circuit area II′. The first bonding pads 120a, 120b, 120c, . . . are electrically connected to the active matrix device 110, and the first bonding pads 120a, 120b, 120c, . . . and the second bonding pads 130a, 130b, 130c, . . . are electrically connected to the driving chip.
As described above, the first bonding pad 120a at the left side of FIG. 1 is electrically connected to the test signal pad 160. Thus, when the first bonding pads 120a, 120b, 120c, . . . and the second bonding pads 130a, 130b, 130c, . . . are bonded with the driving chip, the electrical property between the first bonding pad 120a and the driving chip can be understood through a test signal on the test signal pad 160, so that the bonding state between the first bonding pad 120a and the driving chip can be determined. However, the test signal pad 160 can only test the bonding state between the first bonding pad 120a and the driving chip while the bonding states between the first bonding pads 120b, 120c, . . . and the driving chip cannot be determined.